Synthetic radio maps of CME-driven shocks below 4 solar radii heliocentric distance

Abstract

We present 2 1/2 D numerical MagnetoHydroDynamic (MHD) simulations of coronal mass ejections (CMEs) in conjunction with plasma simulations of radio emission from the CME-driven shocks. The CME-driven shock extends to an almost spherical shape during the temporal evolution of the CME. Our plasma simulations can reproduce the dynamic spectra of coronal type n radio bursts, with the frequency drift rates corresponding to the shock speeds. We find further, that the CME-driven shock is an effective radio emitter at metric wavelengths, when the CME has reached a heliocentric distance of about two solar radii (R ⊙). We apply our simulation results to explain the radio images of type II bursts obtained by radio heliographs, in particular to the banana-shaped images of radio sources associated with fast CMEs.